In many industrial uses, a plurality of threaded connection elements such as bolts are employed for fastening a component removably to an appliance.
This applies particularly to pressurized vessels used in industry, especially the nuclear industry, for example the vessels of nuclear reactors, or the chemical or petrochemical industry, where a cover is fastened removably to a vessel so that work can be carried out periodically in the vessel.
For this purpose, the cover is fastened to the vessel by means of bolts which are screwed into internally-threaded holes provided in the upper part of the vessel and which penetrate into open-ended bores provided in the flange of the cover and corresponding to the internally threaded holes.
These bolts are generally used in somewhat large numbers and relatively close to one another, and a pull is usually exerted on each bolt by means of a tension devices, for the purpose of keeping it in a prestressed device state, and while this pull is being exerted a clamping nut is screwed or unscrewed.
In some cases, the bolts are of the short type, and therefore to exert on these bolts the pull necessary to keep them in a prestressed state at the moment of screwing or unscrewing of the clamping nut, it is essential to screw an extension piece onto the free end of each bolt.
Each extension piece is screwed onto a connection element by means of a supporting module which bears on the component to be fastened and which for this purpose comprises means for driving the extension piece in rotation, in order to screw it onto or unscrew it from the connection element, and means for tensioning the threaded connection element.
This supporting and extending module consists of a one-piece assembly which makes it possible generally to position two extension pieces and to tension two connection elements simultaneously by means of these extension pieces.
However, this system constitutes a rigid assembly which is difficult to manipulate and position in order to align each extension piece with the corresponding threaded connection element, and therefore the screwing of the extension pieces very often causes flanging which can prevent screwing or cause a seizure, because of the error of alignment attributable to the fact that the module is positioned askew on the component to be fastened.
In the past, the alignment has been obtained by adjusting the a position of each extension piece manually, but this is far from satisfactory where repetitive operations are carried out, for example, in an irradiated environment.